Tue, Aug 03, 2021:On Demand
Background/Question/Methods
Abundance occupancy relationships predict that species distributions are linked to their local abundance, such that species with relatively greater distributions across a landscape will also have relatively higher local abundances. However, the extent to which this relationship is true temporally, or how both spatial and temporal patterns relate to abundance is not understood. This provides an interesting test of theory. Does occupancy relate similarly to abundance across both space and time? We predict that species that occur more often (either spatially or temporally) across a landscape will have higher local abundance. Further, we expect that species with both high spatial and temporal occupancy will have the highest local abundances.
We investigated if and how abundance occupancy relationships exist for small mammal species in the United States using the NEON dataset. For both the spatial and temporal analyses local abundance was defined as the mean monthly site abundance, standardized by sampling effort. Species spatial occupancy was quantified as the proportion of sites where the species was detected. Temporal occupancy was quantified as the mean proportion of months detected across sites, weighted by sampling effort.
Results/Conclusions Varied abundance occupancy patterns were found for both spatial and temporal relationships. As predicted, species with high abundances tended to have either high spatial or temporal occupancies, or both. However, in several instances of high abundance there were disparities between spatial and temporal patterns, specifically with higher temporal occupancy than spatial. In general, species exhibited a broader range of temporal occupancy relative to spatial, as few species occupied all sites. These findings highlight the significance of temporal patterns in species abundance and lend support to the observed relationships between occupancy and abundance. Additionally, these results suggest a potential mechanism by which outliers of the traditional abundance occupancy relationship may be exhibiting higher than expected levels of abundance. Future research is needed to explore how spatial and temporal patterns may interact across scales, and how these relationships are influenced by habitat, trait variability, and phenological dynamics.
Results/Conclusions Varied abundance occupancy patterns were found for both spatial and temporal relationships. As predicted, species with high abundances tended to have either high spatial or temporal occupancies, or both. However, in several instances of high abundance there were disparities between spatial and temporal patterns, specifically with higher temporal occupancy than spatial. In general, species exhibited a broader range of temporal occupancy relative to spatial, as few species occupied all sites. These findings highlight the significance of temporal patterns in species abundance and lend support to the observed relationships between occupancy and abundance. Additionally, these results suggest a potential mechanism by which outliers of the traditional abundance occupancy relationship may be exhibiting higher than expected levels of abundance. Future research is needed to explore how spatial and temporal patterns may interact across scales, and how these relationships are influenced by habitat, trait variability, and phenological dynamics.